Methods and apparatus for host register access for data storage controllers for ongoing standards compliance

ABSTRACT

The present disclosure describes technologies and techniques for use by a data storage controller (such as a non-volatile memory (NVM) controller) to emulate hardware registers in software and/or firmware. In illustrative examples, an arbiter of the NVM controller arbitrates inbound register accesses from a host. Regular register accesses from the host are directed by the arbiter along a regular hardware read path within the NVM controller to physical memory registers. Other transactions (e.g. writes to, or reads from, an undefined or reserved address space) are instead directed by the arbiter to the processor of the NVM controller for handling by software running on the processor (and/or by firmware). In this manner, new hardware registers added to an NVM standard may be implemented by software and/or firmware rather than hardware. Hence, the NVM controller may comply with new standard requirements without changing the hardware. NVMe examples are provided.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

The present Application for Patent claims priority to U.S. ProvisionalApplication No. 62/643,660 entitled “METHODS AND APPARATUS FOR HOSTREGISTER ACCESS FOR DATA STORAGE CONTROLLERS FOR ONGOING STANDARDSCOMPLIANCE” filed Mar. 15, 2018, and to U.S. Provisional Application No.62/683,491, also entitled “METHODS AND APPARATUS FOR HOST REGISTERACCESS FOR DATA STORAGE CONTROLLERS FOR ONGOING STANDARDS COMPLIANCE,”filed Jun. 11, 2018, both of which are fully incorporated by referenceherein.

FIELD

The subject matter described herein relates to data storage devices andcontrollers. More particularly, the subject matter relates, in someexamples, controlling access by a host to registers within a datastorage controller of a non-volatile memory express (NVMe) system.

INTRODUCTION

Solid state devices (SSDs) that incorporate non-volatile memories(NVMs), such as flash NAND memories, are rapidly replacing orsupplementing conventional rotating hard disk drives for mass storage inmany consumer electronics and computers. In NAND-based products, a hostdevice such as a videocamera or other portable electronic deviceincludes an NVM data storage controller for accessing the NAND. Variousindustry standards have been developed to facilitate the development andstandardization of such devices. One such standard is the non-volatilememory express (NVMe) system provided for use with systems that utilizePeripheral Component Interconnect (PCI) Express-based solid statedrives. See, for example, the NVM Express standard, Revision 1.3a, Oct.24, 2017.

Issues may arise in the development and design of NVM data storagecontrollers if the particular standard changes (as might occur withpossible forthcoming revisions to the NVMe standard, e.g., a Revision1.4, a Revision 1.5, etc.) To accommodate changes in an NVMspecification, such as changes in the NVMe requirements, any applicationspecific integrated circuits (ASICs) employed by the NVM data storagecontroller may need to be redesigned. Generally speaking, the ASICdevelopment process may be separated into two aspects: the hardware andthe software. The hardware is manufactured and made final, while thesoftware may change over time in order to fit a specific product'srequirements, e.g. the requirements of a particular data controller.During the development phase, a product specification is defined.However, over time the requirements may change. Often, to support newfeatures set forth in a revision of a particular standard, such as achange from one NVMe Revision to the next NVMe Revision, new hardwaremay need to be designed and tested, which can be an expensive andtime-consuming process.

It would be desirable to provide solutions to these and other issuesthat can be implemented within NVM data storage controllers (and othersimilar devices).

SUMMARY

One embodiment of the present disclosure provides a method for use by adata storage controller, the method including: receiving a registeraccess request from a host device directed to a memory register addresswithin a host register memory space of the data storage controller;determining whether or not the register access request is executableusing hardware memory registers of the data storage controller; inresponse to a determination that the register access request isexecutable using the hardware memory registers of the data storagecontroller, executing the register access request using a correspondingmemory register of the data storage controller; and in response to adetermination that the register access request is not executable usingthe hardware memory registers of the data storage controller, executingthe register access request using a processor of the data storagecontroller.

Another embodiment of the present disclosure provides a data storagecontroller, where the data storage controller includes: a processor; oneor more memory registers; and a processing component configured toreceive a register access request from a host device directed to amemory register address within a host register memory space of the datastorage controller; and determine whether the register access request isexecutable using the one or more hardware memory registers, and if so,execute the register access request using a corresponding memoryregister of the data storage controller, and, if not, execute theregister access request using the processor of the data storagecontroller.

Yet another embodiment of the present disclosure provides a data storagecontroller, where the data storage controller includes: a processor; oneor more hardware memory registers; a register access request inputcontroller configured to receive a register access request from a hostdevice directed to a memory register address within a host registermemory space of the data storage controller; a determination controllerconfigured to determine whether or not the register access request isexecutable using the one or more hardware memory registers; a hardwareexecution routing circuit configured to route the register accessrequest to the hardware memory registers for execution using acorresponding memory register in response to a determination that theregister access request is executable using the one or more hardwarememory registers; and a processor execution routing circuit configuredto route the register access request to the processor for executionusing the processor in response to a determination that the registeraccess request is not executable using the one or more hardware memoryregisters.

Yet another embodiment of the present disclosure provides an apparatusfor use with a data storage controller, comprising: means for receivinga register access request from a host device directed to a memoryregister address within a host register memory space of the data storagecontroller; means for determining whether the register access request isexecutable using hardware memory registers of the data storagecontroller; and means, responsive to a determination that the registeraccess request is executable using hardware memory registers of the datastorage controller, for executing the register access request using acorresponding memory register of the data storage controller, and forexecuting the register access request using a processor of the datastorage controller otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter described herein will now be explained with referenceto the accompanying drawings of which:

FIG. 1 illustrates a system having a data storage controller and a datastorage device (such as a NAND), where the data storage controller isequipped to process certain memory register transaction requests from ahost using software and/or firmware rather than hardware.

FIG. 2 is a flow chart summarizing exemplary operations that may beperformed by an NVM data storage controller to distinguish betweennormal memory register requests for sending to hardware registers andspecial requests for handing via software and/or firmware.

FIG. 3 is another flow chart summarizing exemplary operations that maybe used by an NVM data storage controller to process memory registerrequests from a host to reserved memory addresses within the NVM datastorage controller.

FIG. 4 is a flow chart summarizing an overall procedure for implementingrevisions to a particular standard or specification that affect hostmemory registers maintained with an NVM data storage controller.

FIG. 5 illustrates a data storage system equipped for use with NVMe,where the NVMe data storage controller is equipped to process certainNVMe memory register transaction requests from a host using softwareand/or firmware rather than hardware.

FIG. 6 illustrates a set of exemplary NVMe host memory registersmaintained within an NVMe data storage controller.

FIG. 7 is a block diagram summarizing selected features of a datastorage controller equipped to process certain memory registertransaction requests from a host using software and/or firmware ratherthan hardware.

FIG. 8 is a block diagram summarizing further selected features of adata storage controller equipped to process certain memory registertransaction requests from a host using software and/or firmware ratherthan hardware.

FIG. 9 is a block diagram summarizing still more selected features of adata storage controller equipped to process certain memory registertransaction requests from a host using software and/or firmware ratherthan hardware.

FIG. 10 is a flow chart summarizing selected operations of a datastorage controller or other suitable device equipped to process certainmemory register transaction requests from a host using software and/orfirmware rather than hardware.

FIG. 11 is a flow chart summarizing other selected operations of a datastorage controller or other suitable device equipped to process certainmemory register transaction requests from a host using software and/orfirmware rather than hardware.

FIG. 12 is a flow chart summarizing still other selected operations of adata storage controller or other suitable device equipped to processcertain memory register transaction requests from a host using softwareand/or firmware rather than hardware.

FIG. 13 is a flow chart summarizing still yet other selected operationsof a data storage controller or other suitable device, which distinguishbetween different types of register access requests based, at least inpart, on a memory register area attribute or parameter.

FIG. 14 is a flow chart summarizing still other selected operations of adata storage controller or other suitable device, which distinguishbetween different types of register access requests based, at least inpart, on a transaction size attribute or parameter.

FIG. 15 is a flow chart summarizing additional selected operations of adata storage controller or other suitable device, which distinguishbetween different types of register access requests based, at least inpart, on access type attribute or parameter.

FIG. 16 is a flow chart summarizing additional selected operations of adata storage controller or other suitable device, which processesregister access requests based on whether the requests are unmapped orreserved within a host register memory space.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part thereof. In addition to theillustrative aspects, embodiments, and features described above, furtheraspects, embodiments, and features will become apparent by reference tothe drawings and the following detailed description. The description ofelements in each figure may refer to elements of proceeding figures.Like numbers may refer to like elements in the figures, includingalternate embodiments of like elements.

Overview

Aspects of the present disclosure provide various apparatus, devices,systems and methods for controlling host access to memory registersusing a data storage controller. The main examples herein relate to datastorage devices or data storage apparatus, where the device or apparatusmay be a solid state device (SSD) such as a solid state drive. In manyexamples, the SSD includes a non-volatile memory (NVM) such as a NANDarray. Some examples herein relate to NVM storage systems configured foruse with the NVM Express (NVMe) system, wherein an NVM data storagecontroller (i.e. a device controller) is configured to control access toan NVM such as a NAND using NVMe protocols. See, again, the NVM Expressstandard, Revision 1.3a, Oct. 24, 2017. However, aspects describedherein are applicable to other data storage systems or protocols.

As noted in the Introduction Section above, issues may arise in thedevelopment and design of NVM data storage controllers (such as NVMecontrollers) when the standard changes to support new or differentfeatures. To support new features set forth in a revision of an NVMstandard, new hardware for the data storage controller may need to bedesigned and tested, which can be an expensive and time-consumingprocess. Moreover, changes that might be made in a future version of thestandard cannot be known generally in advance. One challenge, therefore,is to design a data storage controller platform configured so thatunknown future standard changes may be implemented in software and/orfirmware, rather than requiring changes to the hardware. Herein,exemplary systems, methods and apparatus are provided for adding newregisters to a register address space to accommodate new featureswithout changing the controller hardware (especially for use in caseswhere the new features require new hardware registers that are mapped inprevious standard version to reserved address space).

As will be explained, NVM data storage controllers are described hereinthat are configured to emulate hardware registers in software and/orfirmware. In illustrative embodiments, the host memory register addressspace is separated or otherwise distinguished by an arbiter (e.g. amultiplexer component installed within the data storage controller) andall inbound register accesses from the host are arbitrated. Regularregister accesses by the host are directed by the arbiter along aregular hardware read path within the data storage controller. A regularaccess request is an access to a register that is mapped by the datastorage controller to a register address that is not reserved. (Theseregular or normal requests are also referred to herein as requests thatare “executable” using the hardware memory registers of the data storagecontroller.) Other transactions, such as writes to, or reads from, anunmapped/undefined or reserved address space, are instead directed bythe arbiter to the processor of the data storage controller for handlingby software running on the processor or by firmware associated with theprocessor. (These special or non-normal requests are also referred toherein as requests that are “not executable” using the hardware memoryregisters of the data storage controller.) Hence, in one aspect, adetermination is made whether a register access request is executableusing hardware memory registers of the data storage controller, and ifso, the register access request is executed using a corresponding memoryregister of the data storage controller, and, if not, the registeraccess request is executed using a processor of the data storagecontroller.

In this manner, new host standard registers (added due to changes in thestandard, such as changes to the NVMe standard) may be implemented viasoftware (and/or firmware) rather than hardware. The software and/orfirmware emulates the functions of the new standard registers. As such,the data storage controller is capable of complying with new standardrequirements (or other changes that might affect the memory registers)without a need to change the hardware of the data storage controller.

Herein, a memory register address is considered to be “mapped” if thedata storage controller is configured to associate a logical addressprovided by the host with a physical register within the memory of thedata storage controller. A mapped address is therefore allocated to thehost for access by the host. An “undefined” or “unmapped” memoryregister address is an address that is not mapped or associated with aphysical register within the memory of the data storage controller. Amapped address is therefore not allocated to the host. A memory registeraddress is considered herein to be “reserved” if it is mapped tophysical address but has no defined or specified function. A reservedaddress is therefore allocated to the host but has no currentlyspecified function. An “unreserved” address is a mapped address that hasa specified function. That is, a reserved address is one that isallocated to the host and has a specified or defined function. Memoryaccess requests that are mapped and not reserved are considered hereinto be executable by the hardware memory registers. Memory accessrequests that are unmapped or are mapped to a reserved address areconsidered herein to be not executable by the hardware memory registers,and hence are sent to the processor.

A register access request directed to a memory register address that ismapped and not reserved within the physical memory of the data storagecontroller also may be referred to herein as a request of a first type(i.e. executable). A register access request directed to a memoryregister address that is either unmapped (undefined) or is reservedwithin the physical memory of the data storage controller may bereferred to herein as a request of a second type (i.e. non-executable).Furthermore, note that, in accordance with the hardware registeremulation systems and procedures described herein, the host may view aparticular memory address as being unreserved (because the host isprogrammed with a newer version of specification), whereas the hardwareof the data storage controller may view the same memory address as beingreserved (because the hardware of the data storage controller wasconfigured under an older version of the specification when the addresswas still reserved).

Exemplary Data Storage Controller Embodiments

FIG. 1 illustrates, at a high level, a data storage system 100configured to controlling access to a data storage device (such as anNVM employing NAND technology) 102 by a host device 104. For a NANDwrite operation, the data storage system 100 receives data from the hostdevice 104 and stores the data in the data storage device 102 under thecontrol of a data storage controller 106 (which may also referred to asa memory controller). The controller 106 and its components may beconfigured using any suitable technology and may be, for example, aphysical hardware circuit or a logical controller formed of functionalmodules. Data and commands may be routed between the data storagecontroller 106 and the data storage device 102 along an internal bus108. Data and commands may be routed between the host device 104 and thedata storage controller 106 along an external bus 110. These operationsmay be operated under the control of a processor 112. In addition tocontrolling the reading/writing of data from/to the NAND 102, the datastorage controller 106 controls access by the host to physical memoryregisters 116 within the data storage controller 106. As shown, anarbiter 114 is provided within the data storage controller 106 thatreceives register access requests or transactions from the host (via bus110 and various intervening components, such as a PCIe/MAC/PHYinterface, discussed below) and determines whether the transactionsshould be sent directly to the registers 116 via normal hardware accesschannels (as is the usual case) or should be instead routed to theprocessor 112 for special handing via software and/or firmware.

In particular, the arbiter 114 of FIG. 1 determines whether the memoryregister transaction is a “normal” transaction (e.g. the access is to adefined area with a correct transaction size and a correct accesspermission) or a “special” access transaction (e.g. the access has anunsupported transaction size or is to a reserved area of memory or theaccess is seeking to write to a read-only register). If the transactionis a normal “first type” transaction, the transaction is sent to theregisters 116 via the normal access channels. If the transaction is aspecial “second type” transaction, the transaction is sent to theprocessor 112 for handling by software running on the processor. Theprocessor 112 decides or determines how to respond to the specialrequest by analyzing transaction information received from the arbiter114. If the data storage controller determines that the memory registertransaction is a normal transaction, the transaction is thereforedetermined to be executable by the hardware registers. If the datastorage controller determines that the memory register transaction is aspecial transaction, the transaction is therefore determined to not beexecutable by the hardware registers.

By way of example, the access request (transaction) may include anattribute, parameter, or other suitable information (herein referred toas a memory register area attribute) that designates or isrepresentative of the area of memory the transaction is direct to. Ifthe memory access area attribute designates a memory area that is (a)mapped within a defined memory space of the data storage controller andis (b) not designated as reserved, then the access request (transaction)is deemed to be a normal access attempt (e.g. “first type”). As such,the access request (transaction) is handled by hardware. If the memoryaccess area attribute instead designates a memory area that is (a) notwithin the memory area mapped within the defined memory space or (b)designates a memory area that is marked as reserved, then the accessrequest (transaction) is deemed to be a non-standard (special) accessattempt (e.g. “second type”). As such, the access request (transaction)is handled by the processor.

As another example, the access request (transaction) may include anattribute, parameter, or other suitable information (herein referred toas a transaction size attribute) that designates or is representative ofthe size of transaction (e.g. the number of bytes or pages). If thetransaction size attribute designates a size that is a permissible (i.e.supported) transaction size, then the access request (transaction) isdeemed to be a normal access attempt (e.g. “first type”) and is handledby hardware. If the transaction size attribute instead designates a sizethat is not permissible (e.g. too large or a size that is otherwiseunsupported), then the access request (transaction) is deemed to be anon-standard (special) access attempt (e.g. “second type”) and is routedto the processor for special handling.

As yet another example, the access request (transaction) may include anattribute, parameter, or other suitable information (herein referred toas an access permission attribute) that designates or is representativeof a type of access that the transaction seeks (e.g. read access orwrite access, for which permission might be needed). If the access typeattribute designates a type of transaction that is permissible (such asa read to a read-only register), then the access request (transaction)is deemed to be a normal access attempt (e.g. “first type”) and ishandled by hardware. If the permission attribute instead designates atype of transaction that is not permissible (e.g. a write to a read-onlyregister), then the access request (transaction) is deemed non-standard(special) (e.g. “second type”) and is routed to the processor forspecial handling.

FIG. 2 summarizes some of these features via a flowchart 200. Briefly,at block 202, the data storage controller receives a host access request(transaction) from the host to a host protocol register space anddetermines if the access is normal or special (by, for example, usingthe criteria noted above). A special transaction may be any transactionthat has parameters that indicate that the corresponding hardwareregister functionality might have changed from a previous version (suchas a transaction addressed to a previously-reserved portion of registermemory). The determination at block 202 may be made by theaforementioned arbiter. If, at decision block 204, the access isdetermined to be normal, then, at block 206, the hardware of the datastorage controller processes or otherwise handles the transaction byaccessing the internal register database via normal channels. Otherwise,beginning at block 208, the processor of the data storage controllerhandles the transaction. That is, at block 208, the processor isnotified of the non-normal (special) transaction and obtains allattributes of the transaction. At block 210, firmware and/or softwarewithin of the data storage controller determines how to respond to thetransaction (based on the data, error flags, etc.) and notifies thehardware of the data storage controller. At block 212, the hardware ofthe data storage controller completes (i.e. terminates) the transactionbased on attributes provided by the processor (i.e. the hardwarereceives any information from the software and/or firmware needed tocomplete the transaction back to the host).

As noted, at block 210, the firmware and/or software within of the datastorage controller determines how to respond to the transaction that wasrouted to the processor. Consider a simplified example where a hardwarespecification has first and second releases, e.g. Version 1 and Version2. The hardware registers of the data storage controller are configuredbased in the specifications and requirements of Version 1. Toaccommodate any changes to the registers within Version 2, the software(and/or firmware) of the data storage controller is designed or modifiedto addresses the changes in the hardware registers from Version 1 toVersion 2. For example, the software may employ lookup tables of thelike that provide a software version of the configuration of thehardware registers as specified in Version 2. That is, to accommodateVersion 2, the software of the data storage controller emulates thehardware registers of Version 2 (even though the actual hardware of thedata storage controller remains unchanged from its original version).

For instance, if a transaction is received from a host (where the hostis programmed in accordance with Version 2) and the transaction isdirected to a hardware register that was reserved in Version 1, thetransaction will be routed to the processor of the data storagecontroller by the arbiter (since it is considered a specialtransaction). If the register is still marked as Reserved in Version 2,i.e. no changes have been made to that particular register from Version1 to Version 2, the software will cause the data storage controller torespond by notifying the host that it has erroneously attempted toaccess a reserved register. That is, the software will cause the datastorage controller to respond in the same manner as if the transactionhad been sent via hardware to the reserved register and rejected by thehardware. However, if the register is no longer marked as reserved inVersion 2, but now has been given a function, i.e. a change has beenmade to that particular register from Version 1 to Version 2, thesoftware will cause the data storage controller to respond by performingwhatever function has been specified by Version 2 (by, for example,returning the latest stored values from that register if the transactionwas read transaction). Hence the software will cause the data storagecontroller to respond in the same manner as if the hardware of the datastorage controller had been modified in accordance with Version 2 andthe transaction had been sent via hardware to a hardware registerconfigured in accordance with Version 2. In either case, the emulationoperations of the software/firmware of the data storage controller aretransparent to the host, which will receive the appropriate response asif the hardware registers of the data storage controller were configuredin accordance with Version 2.

FIG. 3 summarizes the scenario just described. Briefly, at block 302,the data storage controller receives a host memory register transactionrequest from the host for a particular register that is Reserved (i.e.the register was designated as Reserved in a prior version of theapplicable standard/specification that matches the current registerdatabase hardware). At block 304, the arbiter of the data storagecontroller routes the transaction request to the processor of the datastorage controller so that software/firmware can determine whether thecorresponding register is still reserved in the current version of thestandard/specification. If the register is still reserved, as determinedat decision block 306, the software/firmware responds, at block 308, bycontrolling the data storage controller to notify the host that it haserroneously attempted to access a reserved register. However, if theparticular register is no longer reserved and has been assigned afunction, the software/firmware responds, at block 310, by controllingthe data storage controller to perform whatever function has beenspecified in the current version of the standard/specification for thatparticular register (by, e.g., returning the latest stored values fromthat register if the transaction is a read transaction).

For the particular example of NVMe Revision 1.3, a request to write to areserved area is ignored by the data storage controller withoutreturning an error, and a read request from the same address returnszeros without returning an error. Hence, in a hypothetical Revision 1.4of the NVMe standard, if a request is made by the host to write to anarea that is still reserved under Revision 1.4, the software/firmware ofthe data storage controller would respond in the same manner as inRevision 1.3 by ignoring writes and returning all zeros for reads.However, if the hypothetical Revision 1.4 changes a particular registerfrom reserved to unreserved and gives that register a function, thesoftware/firmware would respond accordingly by, for example, looking upthe appropriate response for Revision 1.4 from its lookup tables. Forinstance, a request to write to a new configuration register(implemented within a previously-reserved area) results with the datastored in a software-controlled database (and with the firmware actingaccordingly), so that a read request from the same address then returnsthe last written value (as expected by the host). A request to write toa new read-only register (implemented within a previously-reserved area)may be ignored without returning an error and so a read request from thesame address would return the relevant internal status.

As another general example, if a transaction is received from a Version2 host that is directed to a portion of memory that was undefined inVersion 1, the transaction will be routed to the processor of the datastorage controller and, if the portion of memory is still undefined inVersion 2, the software will cause the data storage controller torespond by notifying the host that is has erroneously attempted toaccess undefined memory. However, if the portion of memory is nowdefined within the register memory space of Version 2, the software willcause the data storage controller to respond by performing whateverfunction has been specified/defined for that new register in Version 2.Hence, the software will here again cause the data storage controller torespond in the same manner as if the hardware of the data storagecontroller had been modified in accordance with Version 2 and thetransaction had been sent via hardware to a hardware register configuredin accordance with Version 2.

Similar logic may be applied in cases where the arbiter routestransactions to the processor if the transaction has an “unsupportedtransaction size” (which may have been unsupported in Version 1 but isnow supported in Version 2) or the transaction seeks to write to a“read-only register” (which may have been “read-only” in Version 1 butis now “read/write” in Version 2). In each case, the software and/orfirmware of the data storage controller determines the appropriateresponse under Version 2 and responds accordingly. Moreover, the samelogic may be applied to further revisions to the applicablespecification (Version 3, Version 4, etc.) with the software/firmware ofthe data controller being updated for each new version (by theengineers/designers of the data storage controller) to address anyhardware register changes via the aforementioned software emulationusing lookup tables of the like. As explained, this may be far lessexpensive than modifying the hardware of the data storage controller toaddress each new revision to the applicable specification or standarddocument.

In an alternative implementation, revisions involving reserved fieldsmay be handled inside an already-defined register. For example, aninternal configuration register may be maintained within the datastorage controller to hold configuration fields for each reserved bit inexisting standard registers that are already defined. Each configurationfield defines or specifies how to handle accesses to its correspondingbit, the access of which may be controlled, at least partially, bysoftware and/or firmware.

As can be appreciated, some modifications of a specification or standarddocument from one version to another might not be of a type or naturethat can be detected by the arbiter or emulated via software and/orfirmware. For example, a particular register specification may bechanged in such a way that transactions to that register would not bedetected by the arbiter (because, e.g., the particular change would notaffect the transaction size or read/write attributes). In such cases,the hardware of the data storage controller is instead modified byengineers/designers to address the changes to the standards. That is,for each new revision to a specification affecting the hardwareregisters, the engineers/designers of the data storage controller mayreview the particular changes in the specification to determine if thechanges can be accommodated using the emulation techniques describedherein. If the changes can be accommodated, the engineers/designersreprogram the software and/or firmware accordingly, thus avoiding theneed to change the hardware of the data storage controller. If anychanges cannot be accommodated, the engineers/designers may redesign thehardware as needed (while also reprogramming the software and/orfirmware, if needed, to conform to the new hardware). Moreover, to avoidtransaction timeouts from the host side, the data storage controllershould be configured to complete any requests within the transactiontimeout of the host. Hence, in some cases, it may be appropriate tomodify the hardware of the data storage controller, rather thanimplement software and/or firmware emulation, to ensure that hosttimeouts are avoided.

Using this general strategy, over the lifecycle of a particularstandard, several revisions (perhaps spanning a period of many years)might be accommodated in a data storage controller via software/firmwareupgrades before a hardware upgrade might be needed to accommodate moresignificant hardware changes. For some standards, and for some devices,all revisions might be accommodated in this manner over the lifetime ofthe standard.

FIG. 4 summarizes this overall revision strategy via flowchart 400.Briefly, at 402, engineers/designers at a company that builds datastorage controllers design the hardware, software and firmware of a newdata storage device (or other device) for use with hardware registers inaccordance with a current standard/specification document and deploy thedevice. If the standard/specification is revised (e.g. from Version 1 toVersion 2), the engineers/designers then determine, at block 404,whether or not revisions to hardware registers of the device can beaccommodated via software/firmware emulation in the device rather thanhardware modifications. That is, the engineers/designers determinewhether the procedures of FIG. 2 can be implemented where an arbiterdirects some host register request transactions to the processor forhandling by software/firmware. If the revisions can be accommodated, asdetermined at decision block 406, the engineers/designers modify thesoftware/firmware of the device, at block 408, to emulate the operationsof any revised hardware registers and configure an arbiter (ormultiplexer) to route corresponding host register transaction requeststo the processor. On the other hand, if at least one revision cannot beaccommodated via software/firmware, then, at block 410, theengineers/designers modify the hardware (and software and firmware, ifneeded) of the device to accommodate the changes to thestandard/specification document. This may require a new read only memory(ROM) or ASIC tape out (where “tape-out” is the final result of thedesign process for ROM-based or ASIC-based NVM controllers before theyare sent for manufacturing). Such a device re-design may also bereferred to as a “re-spin” or “re-spinning” the ROM or ASIC, and can becostly for the NVM controller manufacturer.

Exemplary NVMe Embodiments

FIG. 5 illustrates certain features of an exemplary NVMe architecture inwhich the above-described procedures and components may be implemented.In FIG. 5, a host device 500 may be any suitable computing platformcapable of accessing memory on a storage device using NVMe procedures.For example, host device 500 may be a desktop personal computer, alaptop computer, a tablet computer, a mobile telephone, or a front endto a storage array. The host device 500 includes internal host memory502, which in this example includes host submission and completionqueues 504, data buffers 506 and other memory components 508. The hostdevice 500 may store data in an NVMe storage device 510. The NVMe device510 may be any suitable device that provides non-volatile memory storagefor host device 500 in accordance with NVMe standards. For example, theNVMe device 510 may be a removable storage device, such as a SSD that isremovably connectable to host device 500. In another example, the NVMedevice 510 may be non-removable or integrated within the host device500. In some embodiments, the host device 500 and the NVMe device 510are communicatively connected via a PCIe bus (represented via ingress536 and egress 538).

The NVMe storage device 510 of FIG. 5 includes an NVMe controller 514and non-volatile memory arrays 512. The NVMe device controller 514(which may also be referred to herein as a data storage controller)controls access to the non-volatile memory arrays 512 (such as a NAND).The NVMe controller 514 thus may be a non-volatile memory controllerthat implements or supports the NVMe protocol, and non-volatile memoryarrays 512 may be 2D or 3D NAND flash memory. The NVMe controller 514includes a host protocol registers component 505, which includes ahardware register database (DB) 507 and an arbiter or multiplexer 509.The host protocol register 505 is responsible for handling host accessto the protocol registers 507. Normal transaction requests received fromthe host 500 (via a PHY/PCIe/MAC interface 522) are routed via hardwareto the register DB 507 along line 511. Special transaction requests (asdiscussed above) are instead routed via a line 513 hardware to one ormore processors 516 that provide for emulation of the register DBhardware via software and/or firmware. (Although not shown, separatevolatile random access memory (RAM) or ROM may be used to store softwareand/or firmware). The processor(s) 516 are also responsible for theexecution of Frond-End and Back-End tasks.

A command path 517 is responsible for fetching and parsing commands fromthe host 500 (other than register DB transactions) and queuing thecommands internally. This may involve obtaining submission requests froma submission queue of the host queues 504 and routing those requests toa flash interface module 532. In addition, the command path 517 isresponsible for the arbitrating and executing the commands A controlpath 518 is responsible for handling control messages delivered from thehost 500 to the device 510 and vice versa. Among other functions, thecontrol path 518 includes a completion queue manager (not shown) thatroutes completion entries received from a scheduler 520 to a completionqueue within host queues 504 of the host device 500 via the PCIe/MAC/PHYinterface 522. Actual pages of data to be delivered to the host device500 (such as the result of read commands from arrays 512) are deliveredusing one or more DMAs 526. Additional components of the NVMe controller514 include the flash interface module 532, which is responsible forcontrolling and accessing the memory arrays 512, and an error correctionmodule 534, which is responsible for error correction. Ingress andegress from the NVMe device 510 is illustrated via arrows 536 and 538.

Note that, in an exemplary implementation, the only components that aremodified relative to conventional NVMe device controller are the hostprotocol registers component 505 and the processor(s) 516 (as well asthe software/firmware associated with the processors). Thenormal/special processing procedures described herein that serve toemulate hardware register revisions to NVMe standards are otherwisetransparent to all other components of the NVMe device 510, as well asthe host device 500. That is, only minimal changes are made to otherwisestandard NVMe systems to implement the host submission queue throttling.

FIG. 6 illustrates NVMe registers 600 that may be stored or maintainedin register database 507 of FIG. 5 for the example of Revision 1.3 ofNVMe. That is, FIG. 6 illustrates register mapping as per NVMe Revision1.3. Boot partition registers are present in this version, while in theprevious standard version (Revision 1.2), the address space 40h to 50hwas a reserved area. Without the SW/FW emulation procedures andcomponents described herein, a product developed with hardware toimplement Revision 1.2 (or earlier) would not be able to support theboot partition feature of Revision 1.3 without a hardware redesign.However, by using the aforementioned SW/FW emulation procedures, thehardware of the device need not be changed to implement the bootpartition feature, only its software/firmware. Future versions of NVMemight exploit the memory area at offset 0x18 for new functions, whichmay then be addressed with appropriate SW/FW emulation procedures ratherthan hardware changes.

Thus, methods and apparatus have been described that provide forpermitting current NVM products to support future versions of a hoststandard and, in some cases, for implementing new features via firmware.Often, firmware changes are enough to avoid a full ASIC tape-out. Theprocedures described herein thus may serve to reduce significantly thetime to market, since ASIC tape-out can be a long process. Moreover, thetechniques may reduce expenses for a full tape-out, which can besubstantial.

Further Exemplary Methods and Embodiments

FIGS. 7-16 illustrate and summarize various general features ofexemplary data storage controllers and methods, or procedures for usewith data storage controllers.

FIG. 7 shows an exemplary data storage controller 700 (or memorycontroller or device controller) configured to communicate with a hostdevice 702 and a data storage device 704, wherein the data storagecontroller 700 may access the data storage device 704 based on commandsissued to the data storage controller 700 by the host device 702.Although many examples described herein relate to NVMe controllers forstoring data within NAND devices, the data storage device 704 may be anysuitable memory or storage device and is not limited to NANDs, and thedata storage controller 700 may be any suitable memory controller deviceand is not limited to NVMe-based controllers.

The exemplary data storage controller 700 of FIG. 7 includes a processor706 and one of more one or more hardware memory registers 708. The datastorage controller 700 also includes a register access requestprocessing component/system 710 having a register access request inputcontroller (e.g. circuit) 712 configured to obtain or receive a registeraccess request from a host device directed to a memory register addresswithin a host register memory space of the data storage controller. Theregister access request processing component/system 710 also includes adetermination controller (e.g. circuit) 714 configured to determinewhether the register access request is executable using the one or moreof the hardware memory registers. The determination controller (e.g.circuit) 714 may correspond, in some examples, to the arbiter 509 ofFIG. 5. The register access request processing component/system 710further includes a hardware execution routing controller (e.g. circuit)716 configured to route or send the register access request to thehardware memory registers 708 for execution using a corresponding memoryregister, if the register access request is executable using one of thehardware memory registers. The register access request processingcomponent/system 710 additionally includes a processor execution routingcontroller (e.g. circuit) 718 configured to route or send the registeraccess request to the processor for execution using the processor, ifthe register access request is not executable using one of the hardwarememory registers.

In at least some examples, means may be provided for performing thefunctions illustrated in FIG. 7 and/or other functions illustrated ordescribed herein. For example, an apparatus (e.g. data storagecontroller 700) may be provided for use with a host device (e.g. host702) and a data storage device (e.g. storage device 704) where theapparatus includes: means (such as controller 712) for obtaining aregister access request from a host device directed to a memory registeraddress within a host register memory space (which, as noted, is amemory space of or within the data storage controller); means (such asdetermination controller 714 or arbiter 509) for determining whether theregister access request is executable using hardware memory registers ofthe data storage controller. Means (such as controller 716) may beprovided for routing or sending the register access request to thehardware memory registers for execution using a corresponding memoryregister, if the register access request is executable using hardwarememory registers. Means (such as controller 718) may be provided forrouting or sending the register access request to the processor forexecution using the processor, if the register access request isexecutable using hardware memory registers.

The subject matter described herein may be implemented in hardware,software, firmware, or any combination thereof. As such, the terms“function” “node” or “module” as used herein refer to hardware, whichmay also include software and/or firmware components, for implementingthe feature being described. In one exemplary implementation, thesubject matter described herein may be implemented using a computerreadable medium having stored thereon computer executable instructionsthat when executed by the processor of a computer control the computerto perform steps. Exemplary computer readable media suitable forimplementing the subject matter described herein include non-transitorycomputer-readable media, such as disk memory devices, chip memorydevices, programmable logic devices, and application specific integratedcircuits. In addition, a computer readable medium that implements thesubject matter described herein may be located on a single device orcomputing platform or may be distributed across multiple devices orcomputing platforms. These are just some examples of suitable means forperforming or controlling the various functions.

In at least some examples, a machine-readable storage medium may beprovided having one or more instructions which when executed by aprocessing circuit causes the processing circuit to performing thefunctions illustrated in FIG. 7 and/or other functions illustrated ordescribed herein. For example, instructions may be provided for:obtaining a register access request from a host device directed to amemory register address within a host register memory space (which, asnoted, is a memory space of or within the data storage controller); andfor determining whether the register access request is executable usinghardware memory registers of the data storage controller. Instructionsmay be provided for routing or sending the register access request tothe hardware memory registers for execution using a corresponding memoryregister, if the register access request is executable using hardwarememory registers. Instructions may be provided for routing or sendingthe register access request to the processor for execution using theprocessor, if the register access request is executable using hardwarememory registers.

FIG. 8 shows another exemplary data storage controller 800 (or memorycontroller or device controller) configured to communicate with a hostdevice 802 and a data storage device 804, wherein the data storagecontroller 800 may access the data storage device 804 based on commandsissued to the data storage controller 800 by the host device 802. Theexemplary data storage controller 800 of FIG. 8 again includes aprocessor 806 and one of more one or more hardware memory registers 808.The data storage controller 800 also includes a register access requestprocessing component/system 810 having a register access request inputcontroller (e.g. circuit) 812 configured to obtain or receive a registeraccess request from a host device directed to a memory register addresswithin a host register memory space (of the data storage controller).The register access request processing component/system 810 alsoincludes a determination controller (e.g. circuit) 814 (such as anarbiter or multiplexer) configured to determine whether the registeraccess request is executable using the one or more of the hardwarememory registers. The hardware memory registers 808 include a hardwareexecution controller (e.g. circuit) 816 configured to execute theregister access request, if the register access request is executableusing one of the hardware memory registers. The processor 806 includes aprocessor execution controller (e.g. circuit) 818 configured to executethe register access request using software and/or hardware, if theregister access request is not executable using one of the hardwarememory registers 808.

Means may be provided for performing the functions illustrated in FIG. 8and/or other functions illustrated or described herein. For example, anapparatus (e.g. data storage controller 800) may be provided for usewith a host device (e.g. host 802 device) and a data storage device(e.g. storage device 804) where the apparatus includes: means (such ascontroller 812) for obtaining a register access request from a hostdevice directed to a memory register address within a host registermemory space and means (such as determination controller 814 or arbiter509) for determining whether the register access request is executableusing hardware memory registers of the data storage controller. Means(such as controller 816) may be provided for executing the registeraccess request using a corresponding memory register of the data storagecontroller. Means (such as controller 818) may be provided for executingthe register access request using a processor of the data storagecontroller.

A machine-readable storage medium may be provided having one or moreinstructions which when executed by a processing circuit causes theprocessing circuit to performing the functions illustrated in FIG. 8and/or other functions illustrated or described herein. For example,instructions may be provided for: obtaining a register access requestfrom a host device directed to a memory register address within a hostregister memory space; and for determining whether the register accessrequest is executable using hardware memory registers of the datastorage controller, and if so, for executing the register access requestusing a corresponding memory register of the data storage controller,and, if not, for executing the register access request using a processorof the data storage controller.

FIG. 9 shows yet another exemplary data storage controller 900 (ormemory controller or device controller) configured to communicate with ahost device 902 and a data storage device 904, wherein the data storagecontroller 900 may access the data storage device 904 based on commandsissued to the data storage controller 900 by the host device 902. Theexemplary data storage controller 900 of FIG. 9 includes a processor 906and one of more one or more memory registers 908. The data storagecontroller 900 also includes a register access request processingcomponent/system 910 having a register access request input controller(e.g. circuit) 912 configured to obtain or receive a register accessrequest from a host device directed to a memory register address withina host register memory space (of the data storage controller). Theregister access request processing component/system 910 also includes adetermination controller (e.g. circuit) 914 configured to determinewhether the register access request is of a first type or of a secondtype, wherein (a) a register access request of the first type isdirected to a memory register address that is mapped and not reservedwithin the physical memory of the data storage controller, and wherein(b) a register access request of the second type is directed to a memoryregister address that is either unmapped or reserved within the physicalmemory. Controller 914 may include a component 915 for determining ifthe memory register address (that the request is directed to) is mappedand not reserved within the physical memory of the data storagecontroller, and a component 917 for determining if memory registeraddress (that the request is directed to) is either unmapped or reservedwithin the physical memory. The register access request processingcomponent/system 910 further includes routing controller (e.g. circuit)916 configured to send the register access request to a correspondingmapped memory register if the register access request is of the firsttype and another routing controller (e.g. circuit) 918 configured tosend the register access request to a processor if the register accessrequest is of the second type. The determination controller (e.g.circuit) 914 may correspond, in some examples, to the arbiter 509 ofFIG. 5. The routing controller (e.g. circuit) 916 may include, in someexamples, to the normal request routing line(s) 511 of FIG. 5. Therouting component 918 may include, in some examples, to the specialrequest routing line(s) 513.

Means may be provided for performing the functions illustrated in FIG. 9and/or other functions illustrated or described herein. For example, anapparatus (e.g. data storage controller 900) may be provided for usewith a host device (e.g. host 902) and a data storage device (e.g.storage device 904) where the apparatus includes: means (such ascontroller 912) for obtaining a register access request from a hostdevice directed to a memory register address within a host registermemory space (which, as noted, is a memory space of or within the datastorage controller); means (such as determination controller 914 orarbiter 509) for determining whether the register access request is of afirst type or of a second type, wherein a register access request of thefirst type is directed to a memory register address that is mapped andnot reserved within the physical memory of the data storage controller,and wherein a register access request of the second type is directed toa memory register address that is either unmapped or reserved within thephysical memory of the data storage controller; means (such as routingcontroller 916) for sending the register access request to acorresponding mapped memory register within the data storage controllerif the register access request is of the first type; and means (such asrouting controller 918) for sending the register access request to aprocessor of the data storage controller if the register access requestis of the second type.

The means for determining whether the register access request is of thefirst type or of the second type may include: means for obtaining amemory register area attribute from the register access request; meansfor determining that the register access request is of the first type ifthe memory access area attribute designates a memory area that is (a)mapped within a defined memory space of the data storage controller and(b) not designated as reserved; an means for determining that theregister access request is of the second type if the memory access areaattribute designates a memory area that is (a) not within the memoryarea mapped within the defined memory space or (b) designates a memoryarea that is marked as reserved. The means for determining whether theregister access request is of the first type or of the second type mayinclude: means for obtaining a transaction size attribute from theregister access request; means for determining that the register accessrequest is of the first type if the transaction size attributecorresponds to a permissible transaction size defined within the datastorage controller; and means for determining that the register accessrequest is of the second type if the transaction size attribute does notcorrespond to the permissible transaction size.

The means for determining whether the register access request is of thefirst type or of the second type may include: means for obtaining anaccess type attribute from the register access request; means fordetermining that the register access request is of the first type if theaccess type attribute corresponds to a permissible access within thedata storage controller; and means for determining that the registeraccess request is of the second type if the access type attribute doesnot correspond to the permissible access within the data storagecontroller. The access type attribute may indicate that the registeraccess request is a read request and the permissible access within thedata storage controller to a corresponding mapped physical memoryregister is for read access, where the register access request is thendetermined to be of the first type because the access type attributecorresponds to the permissible access. The access type attribute mayindicate that the register access request is a read request but thepermissible access within the data storage controller to a correspondingmapped physical memory register is for write access, where the registeraccess request is then determined to be of the second type because theaccess type attribute does not correspond to the permissible access.

The apparatus may further include means for processing the registeraccess request using hardware of the data storage controller if theregister access request is sent to the corresponding mapped memoryregister; and means for processing the register access request usingsoftware running on the processor if the register access request is sentto the processor. The means for sending the register access request tothe processor may include means for sending register access requestattributes along with the register access request to the processor. Themeans for processing the register access request using software mayoperate based, at least in part, on the register access requestattributes.

For a register access request that is directed to a register that iseither unmapped or reserved within the physical memory of the datastorage controller, the software may determine whether the register isalso either unmapped or reserved within the host memory space based oninformation programmed into the data storage controller and, if so, thedata storage controller rejects the register access request aserroneous. For a register access request that is directed to theregister that is either unmapped or reserved within the physical memoryof the data storage controller, if the software determines that theregister is mapped within the host memory space, the software of thedata storage controller processes the register access request inaccordance with pre-programmed operations to complete the registeraccess request.

A machine-readable storage medium may be provided having one or moreinstructions which when executed by a processing circuit causes theprocessing circuit to performing the functions illustrated in FIG. 9and/or other functions illustrated or described herein. For example,instructions may be provided for: obtaining a register access requestfrom a host device directed to a memory register address within a hostregister memory space; determining whether the register access requestis of a first type or of a second type, wherein a register accessrequest of the first type is directed to a memory register address thatis mapped and not reserved within the physical memory of the datastorage controller, and wherein a register access request of the secondtype is directed to a memory register address that is either unmapped orreserved within the physical memory of the data storage controller;sending the register access request to a corresponding mapped memoryregister within the data storage controller if the register accessrequest is of the first type; and sending the register access request toa processor of the data storage controller if the register accessrequest is of the second type.

The instructions for determining whether the register access request isof the first type or of the second type may include: instructions forobtaining a memory register area attribute from the register accessrequest; instructions for determining that the register access requestis of the first type if the memory access area attribute designates amemory area that is (a) mapped within a defined memory space of the datastorage controller and (b) not designated as reserved; an instructionsfor determining that the register access request is of the second typeif the memory access area attribute designates a memory area that is (a)not within the memory area mapped within the defined memory space or (b)designates a memory area that is marked as reserved. The instructionsfor determining whether the register access request is of the first typeor of the second type may include: instructions for obtaining atransaction size attribute from the register access request;instructions for determining that the register access request is of thefirst type if the transaction size attribute corresponds to apermissible transaction size defined within the data storage controller;and instructions for determining that the register access request is ofthe second type if the transaction size attribute does not correspond tothe permissible transaction size.

The instructions for determining whether the register access request isof the first type or of the second type may include: instructions forobtaining an access type attribute from the register access request;instructions for determining that the register access request is of thefirst type if the access type attribute corresponds to a permissibleaccess within the data storage controller; and instructions fordetermining that the register access request is of the second type ifthe access type attribute does not correspond to the permissible accesswithin the data storage controller. The access type attribute mayindicate that the register access request is a read request and thepermissible access within the data storage controller to a correspondingmapped physical memory register is for read access, where the registeraccess request is then determined to be of the first type because theaccess type attribute corresponds to the permissible access. The accesstype attribute may indicate that the register access request is a readrequest but the permissible access within the data storage controller toa corresponding mapped physical memory register is for write access,where the register access request is then determined to be of the secondtype because the access type attribute does not correspond to thepermissible access.

The apparatus may further include instructions for processing theregister access request using hardware of the data storage controller ifthe register access request is sent to the corresponding mapped memoryregister; and instructions for processing the register access requestusing software running on the processor if the register access requestis sent to the processor. The instructions for sending the registeraccess request to the processor may include instructions for sendingregister access request attributes along with the register accessrequest to the processor. The instructions for processing the registeraccess request using software may operate based, at least in part, onthe register access request attributes.

For a register access request that is directed to a register that iseither unmapped or reserved within the physical memory of the datastorage controller, the instructions may determine whether the registeris also either unmapped or reserved within a host memory space based oninformation programmed into the data storage controller and, if so, thedata storage controller rejects the register access request aserroneous. For a register access request that is directed to theregister that is either unmapped or reserved within the physical memoryof the data storage controller, if the instructions determines that theregister is mapped within the host memory space, the software of thedata storage controller processes the register access request inaccordance with pre-programmed operations to complete the registeraccess request.

FIG. 10 broadly summarizes exemplary operations 1000 for use by or witha data storage controller or other suitable device to process registeraccess requests. Briefly, at block 1002, the data storage controllerobtains (or receives) a register access request from a host devicedirected to a memory register address within a host register memoryspace of the data storage controller. At block 1004, the data storagecontroller determines whether the register access request is executableusing hardware memory registers of the data storage controller, and ifso, executes the register access request using a corresponding memoryregister of the data storage controller, and, if not, executes theregister access request using a processor of the data storagecontroller.

Means may be provided for performing the functions illustrated in FIGS.7, 9 and 10 and/or other functions illustrated or described herein. Anapparatus (e.g. data storage controller 700) may be provided for usewith a host device (e.g. host 702) and a data storage device (e.g.storage device 704) where the apparatus includes: means (such ascontroller 712) for obtaining a register access request from a hostdevice directed to a memory register address within a host registermemory space (of the data storage controller). Additionally, means (suchas register access request processing component/system 710) may beprovided for determining whether the register access request isexecutable using hardware memory registers of the data storagecontroller, and if so, for executing the register access request using acorresponding memory register of the data storage controller, and, ifnot, for executing the register access request using a processor of thedata storage controller.

Still further, means may be provided, responsive to a determination thatthe register access request is executable using hardware memoryregisters of the data storage controller, for executing the registeraccess request using a corresponding memory register of the data storagecontroller (such as component 716), and that operate for executing theregister access request using a processor of the data storage controllerotherwise (such as component 718). The means for determining whether theregister access request is executable using the hardware memoryregisters may include: means (such as component 915 of controller 914)for determining whether the register access request is directed to amemory register address that is both mapped and not reserved within aphysical memory of the data storage controller; and means (such ascomponent 917 of controller 914) for determining whether the registeraccess request is directed to a memory register address that is eitherunmapped or reserved within the physical memory of the data storagecontroller. Means (such as component 916) may be provided for sendingthe register access request to a corresponding mapped memory registerwithin the data storage controller if the register access request isdetermined to be both mapped and not reserved. Means (such as component918) may be provided for sending the register access request to theprocessor of the data storage controller if the register access requestis determined to be either unmapped or reserved.

Instructions may be provided, which when executed by a processingcircuit causes the processing circuit to perform the functionsillustrated in FIGS. 7, 9 and 10 and/or other functions illustrated ordescribed herein. For example instructions may be provided for:obtaining a register access request from a host device directed to amemory register address within a host register memory space.Instructions may be provided for determining whether the register accessrequest is executable using hardware memory registers of the datastorage controller, and if so, for executing the register access requestusing a corresponding memory register of the data storage controller,and, if not, for executing the register access request using a processorof the data storage controller.

Still further, instructions may be provided, responsive to adetermination that the register access request is executable usinghardware memory registers of the data storage controller, for executingthe register access request using a corresponding memory register of thedata storage controller, and that operate for executing the registeraccess request using a processor of the data storage controllerotherwise. The instructions for determining whether the register accessrequest is executable using the hardware memory registers may include:instructions for determining whether the register access request isdirected to a memory register address that is both mapped and notreserved within a physical memory of the data storage controller; andinstructions for determining whether the register access request isdirected to a memory register address that is either unmapped orreserved within the physical memory of the data storage controller.Instructions may be provided for sending the register access request toa corresponding mapped memory register within the data storagecontroller if the register access request is determined to be bothmapped and not reserved. Instructions may be provided for sending theregister access request to the processor of the data storage controllerif the register access request is determined to be either unmapped orreserved.

FIG. 11 further summarizes exemplary operations 1100 for use by or witha data storage controller or other suitable device to process registeraccess requests. Briefly, at block 1102, the data storage controllerobtains (or receives) a register access request from a host devicedirected to a memory register address within a host register memoryspace of the data storage controller. At block 1104, the data storagecontroller determines whether the register access request is of a firsttype or of a second type, wherein (a) a register access request of thefirst type is directed to a memory register address that is mapped andnot reserved within the physical memory of the data storage controller,and wherein (b) a register access request of the second type is directedto a memory register address that is either unmapped or reserved withinthe physical memory of the data storage controller. (An example of areserved register address is the reserved address shown in FIG. 6). Atblock 1106, the data storage controller sends or routes the registeraccess request to a corresponding mapped memory register within the datastorage controller if the register access request is of the first type,so that the data storage controller processes the register accessrequest using hardware. At block 1108, the data storage controller sendsor routes the register access request to a processor of the data storagecontroller if the register access request is of the second type and,where, for example, register access request attributes are sent alongwith the register access request to the processor, and the processorthen processes the register access request using software and/orfirmware based, at least in part, on the register access requestattributes.

FIG. 12 summarizes still other exemplary operations 1200 for use by orwith a data storage controller or other suitable device to registeraccess requests. Briefly, at block 1202, the data storage controllerreceives a register access request from a host device directed to amemory register address within a host register memory space of (orwithin) the data storage controller, and, at block 1204, the datastorage controller determines whether or not the register access requestis executable using hardware memory registers of the data storagecontroller. At block 1206, in response to a determination that theregister access request is executable using the hardware memoryregisters of the data storage controller, the data storage controllerexecutes the register access request using a corresponding memoryregister of the data storage controller. At block 1208, in response to adetermination that the register access request is not executable usingthe hardware memory registers of the data storage controller, the datastorage controller executes the register access request using aprocessor of the data storage controller. These features were discussedabove.

Means may be provided for performing the functions illustrated in FIG.12 and/or other functions illustrated or described herein. An apparatus(e.g. data storage controller 700) may be provided for use with a hostdevice (e.g. host 702) and a data storage device (e.g. storage device704) where the apparatus includes: means (such as controller 712) forreceiving a register access request from a host device directed to amemory register address within a host register memory space of the datastorage controller; and means (such as controller 714) may be providedfor determining whether or the register access request is executableusing hardware memory registers of the data storage controller. Means(such as controller 716) may be provided for, in response to adetermination that the register access request is executable using thehardware memory registers of the data storage controller, executing theregister access request using a corresponding memory register of thedata storage controller. Means (such as controller 718) may be providedfor, in response to a determination that the register access request isnot executable using the hardware memory registers of the data storagecontroller, executing the register access request using a processor ofthe data storage controller.

Instructions may be provided, which when executed by a processingcircuit causes the processing circuit to perform the functionsillustrated in FIG. 12 and/or other functions illustrated or describedherein. For example instructions may be provided for: receiving aregister access request from a host device directed to a memory registeraddress within a host register memory space of the data storagecontroller. Instructions may be provided for determining whether or notthe register access request is executable using hardware memoryregisters of the data storage controller. Instructions may be providedfor, in response to a determination that the register access request isexecutable using the hardware memory registers of the data storagecontroller, executing the register access request using a correspondingmemory register of the data storage controller. Instructions may beprovided for, in response to a determination that the register accessrequest is not executable using the hardware memory registers of thedata storage controller, executing the register access request using aprocessor of the data storage controller.

FIG. 13 summarizes exemplary operations 1300 for use by or with a datastorage controller or other suitable device, which operate to exploit amemory register area attribute to distinguish between different types ofregister access requests. Briefly, at block 1302, the data storagecontroller obtains a memory register area attribute from a registeraccess request (where, as discussed above, the memory register areaattribute includes parameters or other information that designates or isrepresentative of the area of memory a transaction is direct to). Atblock 1304, the data storage controller determines that the registeraccess request is of a first type if the memory access area attributedesignates a memory area that is (a) mapped within a defined memoryspace of the data storage controller and (b) not designated as reserved.At block 1306, the data storage controller determines that the registeraccess request is of a second type if the memory access area attributedesignates a memory area that is (a) not within the memory area mappedwithin the defined memory space or (b) designates a memory area that ismarked as reserved. At block 1308, the data storage controller sends (orroutes) the register access request to a corresponding mapped memoryregister within the data storage controller if the register accessrequest is of the first type, and sends (or routes) the register accessrequest to the processor of the data storage controller if the registeraccess request is of the second type. These features were discussedabove.

FIG. 14 summarizes exemplary operations 1400 for use by or with a datastorage controller or other suitable device, which operate to exploit atransaction size attribute to distinguish between different types ofregister access requests. Briefly, at block 1402, the data storagecontroller obtains a transaction size attribute from the register accessrequest (where, as discussed above, the transaction size attributeincludes parameters or other information that designates or isrepresentative of a size of the register access transaction). At block1404, the data storage controller determines that the register accessrequest is of a first type if the transaction size attribute correspondsto a permissible transaction size defined within the data storagecontroller. At block 1406, the data storage controller determines thatthe register access request is of a second type if the transaction sizeattribute does not correspond to the permissible transaction size. Atblock 1408, the data storage controller sends (or routes) the registeraccess request to a corresponding mapped memory register within the datastorage controller if the register access request is of the first type,and sends (or routes) the register access request to the processor ofthe data storage controller if the register access request is of thesecond type. These features were discussed above.

FIG. 15 summarizes exemplary operations 1500 for use by or with a datastorage controller or other suitable device, which operate to exploit anaccess type attribute to distinguish between different types of registeraccess requests. Briefly, at block 1502, the data storage controllerobtains an access type attribute from the register access request (wherethe access type attribute designates or is representative of a type ofaccess that the transaction seeks, e.g. read or write, for withpermission might be needed). At block 1504, the data storage controllerdetermines that the register access request is of a first type if theaccess type attribute corresponds to a permissible access within thedata storage controller, and where, for example, the access typeattribute indicates that the register access request is a read request,and the permissible access within the data storage controller to acorresponding mapped physical memory register is for read access, and so(in this example) the register access request is determined to be of thefirst type because the access type attribute corresponds to thepermissible access. At block 1506, the data storage controllerdetermines that the register access request is of a second type if theaccess type attribute does not correspond to the permissible accesswithin the data storage controller, and where, for example, the accesstype attribute indicates that the register access request is a readrequest but the permissible access within the data storage controller toa corresponding mapped physical memory register is for write access andso (in this example) the register access request is then determined tobe of the second type because the access type attribute does notcorrespond to the permissible access. At block 1508, the data storagecontroller sends (or routes) the register access request to acorresponding mapped memory register within the data storage controllerif the register access request is of the first type, and sends (orroutes) the register access request to the processor of the data storagecontroller if the register access request is of the second type. Thesefeatures were discussed above.

FIG. 16 summarizes still other exemplary operations 1600 for use by orwith a data storage controller or other suitable device. Briefly, atblock 1602, for a register access request directed to a register that iseither unmapped or reserved within the physical memory of the datastorage controller, the processor of the data storage controllerdetermines whether the register is either unmapped or reserved within ahost memory space of the data storage controller based on informationprogrammed into the data storage controller. At block 1604, if theregister is found to be either unmapped or reserved within the hostmemory space, the data storage controller rejects the register accessrequest as erroneous. At block 1606, if the register is instead found tobe mapped within the host memory space, the processor of the datastorage controller processes the register access request in accordancewith pre-programmed operations to complete the register access request.These features were discussed above.

The subject matter described herein can be implemented in any suitableNAND flash memory, including 2D or 3D NAND flash memory. Semiconductormemory devices include volatile memory devices, such as DRAM) or staticrandom access memory (SRAM) devices, non-volatile memory devices, suchas resistive random access memory (ReRAM), electrically erasableprogrammable read only memory (EEPROM), flash memory (which can also beconsidered a subset of EEPROM), ferroelectric random access memory(FRAM), and magnetoresistive random access memory (MRAM), and othersemiconductor elements capable of storing information. Each type ofmemory device may have different configurations. For example, flashmemory devices may be configured in a NAND or a NOR configuration.

The memory devices can be formed from passive and/or active elements, inany combinations. By way of non-limiting example, passive semiconductormemory elements include ReRAM device elements, which in some embodimentsinclude a resistivity switching storage element, such as an anti-fuse,phase change material, etc., and optionally a steering element, such asa diode, etc. Further by way of non-limiting example, activesemiconductor memory elements include EEPROM and flash memory deviceelements, which in some embodiments include elements containing a chargestorage region, such as a floating gate, conductive nanoparticles, or acharge storage dielectric material.

Multiple memory elements may be configured so that they are connected inseries or so that each element is individually accessible. By way ofnon-limiting example, flash memory devices in a NAND configuration (NANDmemory) typically contain memory elements connected in series. A NANDmemory array may be configured so that the array is composed of multiplestrings of memory in which a string is composed of multiple memoryelements sharing a single bit line and accessed as a group.Alternatively, memory elements may be configured so that each element isindividually accessible, e.g., a NOR memory array. NAND and NOR memoryconfigurations are exemplary, and memory elements may be otherwiseconfigured. The semiconductor memory elements located within and/or overa substrate may be arranged in two or three dimensions, such as a twodimensional memory structure or a three dimensional memory structure.

In a two dimensional memory structure, the semiconductor memory elementsare arranged in a single plane or a single memory device level.Typically, in a two dimensional memory structure, memory elements arearranged in a plane (e.g., in an x-z direction plane) which extendssubstantially parallel to a major surface of a substrate that supportsthe memory elements. The substrate may be a wafer over or in which thelayer of the memory elements are formed or it may be a carrier substratewhich is attached to the memory elements after they are formed. As anon-limiting example, the substrate may include a semiconductor such assilicon. The memory elements may be arranged in the single memory devicelevel in an ordered array, such as in a plurality of rows and/orcolumns. However, the memory elements may be arrayed in non-regular ornon-orthogonal configurations. The memory elements may each have two ormore electrodes or contact lines, such as bit lines and word lines.

A three dimensional memory array is arranged so that memory elementsoccupy multiple planes or multiple memory device levels, thereby forminga structure in three dimensions (i.e., in the x, y and z directions,where the y direction is substantially perpendicular and the x and zdirections are substantially parallel to the major surface of thesubstrate). As a non-limiting example, a three dimensional memorystructure may be vertically arranged as a stack of multiple twodimensional memory device levels. As another non-limiting example, athree dimensional memory array may be arranged as multiple verticalcolumns (e.g., columns extending substantially perpendicular to themajor surface of the substrate, i.e., in the y direction) with eachcolumn having multiple memory elements in each column. The columns maybe arranged in a two dimensional configuration, e.g., in an x-z plane,resulting in a three dimensional arrangement of memory elements withelements on multiple vertically stacked memory planes. Otherconfigurations of memory elements in three dimensions can alsoconstitute a three dimensional memory array.

By way of non-limiting example, in a three dimensional NAND memoryarray, the memory elements may be coupled together to form a NAND stringwithin a single horizontal (e.g., x-z) memory device levels.Alternatively, the memory elements may be coupled together to form avertical NAND string that traverses across multiple horizontal memorydevice levels. Other three dimensional configurations can be envisionedwherein some NAND strings contain memory elements in a single memorylevel while other strings contain memory elements which span throughmultiple memory levels. Three dimensional memory arrays may also bedesigned in a NOR configuration and in a ReRAM configuration.

Typically, in a monolithic three dimensional memory array, one or morememory device levels are formed above a single substrate. Optionally,the monolithic three dimensional memory array may also have one or morememory layers at least partially within the single substrate. As anon-limiting example, the substrate may include a semiconductor such assilicon. In a monolithic three dimensional array, the layersconstituting each memory device level of the array are typically formedon the layers of the underlying memory device levels of the array.However, layers of adjacent memory device levels of a monolithic threedimensional memory array may be shared or have intervening layersbetween memory device levels.

Then again, two dimensional arrays may be formed separately and thenpackaged together to form a non-monolithic memory device having multiplelayers of memory. For example, non-monolithic stacked memories can beconstructed by forming memory levels on separate substrates and thenstacking the memory levels atop each other. The substrates may bethinned or removed from the memory device levels before stacking, but asthe memory device levels are initially formed over separate substrates,the resulting memory arrays are not monolithic three dimensional memoryarrays. Further, multiple two dimensional memory arrays or threedimensional memory arrays (monolithic or non-monolithic) may be formedon separate chips and then packaged together to form a stacked-chipmemory device.

Associated circuitry is typically required for operation of the memoryelements and for communication with the memory elements. As non-limitingexamples, memory devices may have circuitry used for controlling anddriving memory elements to accomplish functions such as programming andreading. This associated circuitry may be on the same substrate as thememory elements and/or on a separate substrate. For example, acontroller for memory read-write operations may be located on a separatecontroller chip and/or on the same substrate as the memory elements. Oneof skill in the art will recognize that the subject matter describedherein is not limited to the two dimensional and three dimensionalexemplary structures described but cover all relevant memory structureswithin the spirit and scope of the subject matter as described hereinand as understood by one of skill in the art.

While the above descriptions contain many specific embodiments of theinvention, these should not be construed as limitations on the scope ofthe invention, but rather as examples of specific embodiments thereof.Accordingly, the scope of the invention should be determined not by theembodiments illustrated, but by the appended claims and theirequivalents. Moreover, reference throughout this specification to “oneembodiment,” “an embodiment,” or similar language means that aparticular feature, structure, or characteristic described in connectionwith the embodiment is included in at least one embodiment of thepresent disclosure. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” and similar language throughout thisspecification may, but do not necessarily, all refer to the sameembodiment, but mean “one or more but not all embodiments” unlessexpressly specified otherwise. The terms “including,” “comprising,”“having,” and variations thereof mean “including but not limited to”unless expressly specified otherwise. An enumerated listing of itemsdoes not imply that any or all of the items are mutually exclusiveand/or mutually inclusive, unless expressly specified otherwise. Theterms “a,” “an,” and “the” also refer to “one or more” unless expresslyspecified otherwise. Furthermore, as used herein, a phrase referring to“at least one of” a list of items refers to any combination of thoseitems, including single members. By way of example, “at least one of: A,B, or C” is intended to cover A, B, C, A-B, A-C, B-C, and A-B-C, as wellas multiples of the same members (e.g., any lists that include AA, BB,or CC). Likewise, “at least one of: A, B, and C” is intended to cover A,B, C, A-B, A-C, B-C, and A-B-C, as well as multiples of the samemembers. Similarly, as used herein, a phrase referring to a list ofitems linked with “and/or” refers to any combination of the items. As anexample, “A and/or B” is intended to cover A alone, B alone, or A and Btogether. As another example, “A, B and/or C” is intended to cover Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, or A, B, and C together.

Aspects of the present disclosure have been described above withreference to schematic flowchart diagrams and/or schematic blockdiagrams of methods, apparatuses, systems, and computer program productsaccording to embodiments of the disclosure. It will be understood thateach block of the schematic flowchart diagrams and/or schematic blockdiagrams, and combinations of blocks in the schematic flowchart diagramsand/or schematic block diagrams, can be implemented by computer programinstructions. These computer program instructions may be provided to aprocessor of a computer or other programmable data processing apparatusto produce a machine, such that the instructions, which execute via theprocessor or other programmable data processing apparatus, create meansfor implementing the functions and/or acts specified in the schematicflowchart diagrams and/or schematic block diagrams block or blocks.

It should also be noted that, in some alternative implementations, thefunctions noted in the block may occur out of the order noted in thefigures. For example, two blocks shown in succession may, in fact, beexecuted substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. Other steps and methods may be conceived that are equivalentin function, logic, or effect to one or more blocks, or portionsthereof, of the illustrated figures. Although various arrow types andline types may be employed in the flowchart and/or block diagrams, theyare understood not to limit the scope of the corresponding embodiments.For instance, an arrow may indicate a waiting or monitoring period ofunspecified duration between enumerated steps of the depictedembodiment.

The various features and processes described above may be usedindependently of one another, or may be combined in various ways. Allpossible combinations and sub-combinations are intended to fall withinthe scope of this disclosure. In addition, certain method, event, stateor process blocks may be omitted in some implementations. The methodsand processes described herein are also not limited to any particularsequence, and the blocks or states relating thereto can be performed inother sequences that are appropriate. For example, described tasks orevents may be performed in an order other than that specificallydisclosed, or multiple may be combined in a single block or state. Theexample tasks or events may be performed in serial, in parallel, or insome other suitable manner. Tasks or events may be added to or removedfrom the disclosed example embodiments. The example systems andcomponents described herein may be configured differently thandescribed. For example, elements may be added to, removed from, orrearranged compared to the disclosed example embodiments.

Various details of the presently disclosed subject matter may be changedwithout departing from the scope of the presently disclosed subjectmatter. Furthermore, the foregoing description is for the purpose ofillustration only, and not for the purpose of limitation.

What is claimed is:
 1. A method for use by a data storage controller,comprising: receiving a register access request from a host devicedirected to a memory register address within a host register memoryspace of the data storage controller; determining whether or not theregister access request is executable using hardware memory registers ofthe data storage controller based on whether the memory register addressis mapped or unmapped and whether the memory register address isreserved or not reserved within a physical memory of the data storagecontroller; in response to a determination that the register accessrequest is executable using the hardware memory registers of the datastorage controller, executing the register access request using acorresponding memory register of the data storage controller; and inresponse to a determination that the register access request is notexecutable using the hardware memory registers of the data storagecontroller, executing the register access request using a processor ofthe data storage controller.
 2. The method of claim 1, whereindetermining whether the register access request is executable using thehardware memory registers of the data storage controller based onwhether the memory register address is mapped or unmapped and whetherthe memory register address is reserved or not reserved within aphysical memory of the data storage controller, comprises: determiningwhether the register access request is of a first type or of a secondtype; wherein a register access request of the first type is directed toa memory register address that is both mapped and not reserved withinthe physical memory of the data storage controller; and wherein aregister access request of the second type is directed to a memoryregister address that is either unmapped or reserved within the physicalmemory of the data storage controller.
 3. The method of claim 2, furthercomprising: sending the register access request to a correspondingmapped memory register within the data storage controller if theregister access request is of the first type; and sending the registeraccess request to the processor of the data storage controller if theregister access request is of the second type.
 4. The method of claim 3,wherein sending the register access request to the processor includessending register access request attributes along with the registeraccess request to the processor, and wherein the processor processes theregister access request using software and/or firmware based, at leastin part, on the register access request attributes.
 5. The method ofclaim 4, wherein, for a register access request directed to a registerthat is either unmapped or reserved within the physical memory of thedata storage controller, the processor determines whether the registeris either unmapped or reserved within the host memory space based oninformation programmed into the data storage controller; and wherein, ifthe register is determined to be either unmapped or reserved within thewithin the host memory space, the data storage controller rejects theregister access request.
 6. The method of claim 5, wherein, if theregister is determined to be mapped within the host memory space, theprocessor processes the register access request in accordance withpre-programmed operations to complete the register access request. 7.The method of claim 2, wherein determining whether the register accessrequest is of the first type or of the second type, comprises: obtaininga memory register area attribute from the register access request;determining that the register access request is of the first type if thememory access area attribute designates a memory area that is (a) mappedwithin a defined memory space of the data storage controller and (b) notdesignated as reserved; and determining that the register access requestis of the second type if the memory access area attribute designates amemory area that is (a) not within the memory area mapped within thedefined memory space or (b) designates a memory area that is marked asreserved.
 8. The method of claim 2, wherein determining whether theregister access request is of the first type or of the second type,comprises: obtaining a transaction size attribute from the registeraccess request; determining that the register access request is of thefirst type if the transaction size attribute corresponds to apermissible transaction size defined within the data storage controller;and determining that the register access request is of the second typeif the transaction size attribute does not correspond to the permissibletransaction size.
 9. The method of claim 2, wherein determining whetherthe register access request is of the first type or of the second type,comprises: obtaining an access type attribute from the register accessrequest; determining that the register access request is of the firsttype if the access type attribute corresponds to a permissible accesswithin the data storage controller; and determining that the registeraccess request is of the second type if the access type attribute doesnot correspond to the permissible access within the data storagecontroller.
 10. The method of claim 9, wherein the access type attributeindicates that the register access request is a read request and thepermissible access within the data storage controller to a correspondingmapped physical memory register is for read access; and wherein theregister access request is then determined to be of the first typebecause the access type attribute corresponds to the permissible access.11. The method of claim 9, wherein the access type attribute indicatesthat the register access request is a read request but the permissibleaccess within the data storage controller to a corresponding mappedphysical memory register is for write access; and wherein the registeraccess request is then determined to be of the second type because theaccess type attribute does not correspond to the permissible access. 12.The method of claim 1, wherein executing the register access requestusing the corresponding memory register of the data storage controllerincludes processing the register access request using hardware of thedata storage controller; and wherein executing the register accessrequest using the processor of the data storage controller includesprocessing the register access request using software running on theprocessor and/or firmware associated with the processor.
 13. The methodof claim 1, wherein the data storage controller is coupled to anon-volatile memory (NVM) device, and wherein the data storagecontroller accesses the NVM device based on memory access commandsissued by the host device.
 14. A data storage controller, comprising: aprocessor; one or more hardware memory registers; and a processingcomponent configured to receive a register access request from a hostdevice directed to a memory register address within a host registermemory space of the data storage controller, and determine whether theregister access request is executable using the one or more hardwarememory registers based on whether the memory register address is mappedor unmapped and whether the memory register address is reserved or notreserved within a physical memory of the data storage controller, and ifthe register access request is executable using the one or more hardwarememory registers, execute the register access request using acorresponding hardware memory register of the data storage controller,and, if the register access request is not executable using the one ormore hardware memory registers, execute the register access requestusing the processor of the data storage controller.
 15. The data storagecontroller of claim 14, wherein the processing component includes aninput component configured to input the register access request.
 16. Thedata storage controller of claim 14, wherein the processing componentincludes an arbiter configured to determine whether the register accessrequest is executable using the one or more hardware memory registers.17. The data storage controller of claim 14, wherein the processingcomponent includes routing circuitry to route the register accessrequest to a hardware memory register, if the register access request isexecutable using at least one of the hardware memory registers, and toroute the register access request to the processor, if the registeraccess request is executable using at least one of the hardware memoryregisters.
 18. The data storage controller of claim 14, wherein the datastorage controller is coupled to a non-volatile memory (NVM) device. 19.A data storage controller, comprising: a processor; one or more hardwarememory registers; a register access request input controller configuredto receive a register access request from a host device directed to amemory register address within a host register memory space of the datastorage controller; a determination controller configured to determinewhether or not the register access request is executable using the oneor more hardware memory registers based on whether the memory registeraddress is mapped or unmapped and whether the memory register address isreserved or not reserved within a physical memory of the data storagecontroller; a hardware execution routing circuit configured to route theregister access request to the hardware memory registers for executionusing a corresponding memory register in response to a determinationthat the register access request is executable using the one or morehardware memory registers; and a processor execution routing circuitconfigured to route the register access request to the processor forexecution using the processor in response to a determination that theregister access request is not executable using the one or more hardwarememory registers.
 20. The data storage controller of claim 19, whereinthe determination controller comprises one or more of an arbiter or amultiplexer.
 21. The data storage controller of claim 19, wherein thedata storage controller is coupled to a non-volatile memory (NVM)device.
 22. The data storage controller of claim 21, wherein the datastorage controller is configured to process commands requests from thehost device in accordance with non-volatile memory express (NVMe)protocols.
 23. An apparatus for use with a data storage controller,comprising: means for receiving a register access request from a hostdevice directed to a memory register address within a host registermemory space of the data storage controller; means for determiningwhether the register access request is executable using hardware memoryregisters of the data storage controller based on whether the memoryregister address is mapped or unmapped and whether the memory registeraddress is reserved or not reserved within a physical memory of the datastorage controller; and means, responsive to a determination that theregister access request is executable using hardware memory registers ofthe data storage controller, for executing the register access requestusing a corresponding memory register of the data storage controller,and for executing the register access request using a processor of thedata storage controller otherwise.
 24. The apparatus of claim 23,wherein the means for determining whether the register access request isexecutable using the hardware memory registers, comprises: means fordetermining whether the register access request is directed to a memoryregister address that is both mapped and not reserved within thephysical memory of the data storage controller; and means fordetermining whether the register access request is directed to a memoryregister address that is either unmapped or reserved within the physicalmemory of the data storage controller.
 25. The apparatus of claim 24,further comprising: means for sending the register access request to acorresponding mapped memory register within the data storage controllerif the register access request is determined to be both mapped and notreserved within the physical memory of the data storage controller; andmeans for sending the register access request to the processor of thedata storage controller if the register access request is determined tobe either unmapped or reserved within the physical memory of the datastorage controller.